SUPERHEAVY RESEARCH AT RIKEN

Abstract

At RIKEN (The Institute of Physical and Chemical Research) in Japan, we have performed experiments to study the productions and decays of the heaviest elements produced by one neutron emission channels of 208 Pb and 209 Bi based heavy-ion induced fusion reactions. A gas-filled type recoil separator has been used for collecting evaporation residues of the reactions separating them from high intensity beam particles. The reactions studied were 208 Pb (58 Fe , n )265 Hs , 208 Pb (64 Ni , n ) 271 Ds , 209 Bi (64 Ni , n ) 272 Rg , 208 Pb (70 Zn , n ) 277112, and 209 Bi (70 Zn , n ) 278113. In studies of the first four reactions we have provided the independent confirmations of the productions and their decays of the isotopes, 265 Hs , 271 Ds , 272 Rg , and 277112, as well as the decay properties of their decay daughters, previously studied by Hofmann et al., a group of Gesellschaft für Schwerionenforschung (GSI), Germany. In the last reaction, we observed two decay chains originated from the isotope 278113, assigned firstly by generic correlation of the alpha decay chains connected into the previously known decay of 266 Bh and 262 Db via previously unknown alpha decays of 278113, 274 Rg and 270 Mt .